Combined heat exchanger, heat exchanging system and the optimization method thereof

ABSTRACT

A combined heat exchanger, a heat exchange system, and an optimization method thereof are provided. The heat exchange system includes: an enhanced vapor injection compressor, a condenser, an expansion valve and an evaporator, which are located in a main circuit; wherein the heat exchange system further includes a first branch branched from the main circuit to an vapor injection port of the compressor at a branch point P downstream of the condenser, and a first heat exchange unit and a second heat exchange unit are further provided in the main circuit between the branch point P and the expansion valve; and wherein a refrigerant leaving the condenser is divided at the branch point P into a first portion passing through the first heat exchange unit and the second heat exchange unit from the main circuit, and a second portion passing through the first branch to the vapor injection port.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 17/252,566filed Dec. 15, 2020, which is a National Stage Application ofPCT/US2020/031624 filed May 6, 2020, which claims the benefit of CNApplication No. 201910375088.8, filed on May 7, 2019, the contents ofeach application is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to the field of heat exchange systems,and more particularly, the present disclosure relates to a combined heatexchanger, a heat exchange system, and an optimization method thereofthat are particularly suitable for a refrigeration system for anelectric transport vehicle.

BACKGROUND OF THE INVENTION

A refrigeration system on a transport vehicle may be equipped with anenhanced vapor injection (EVI) compressor. In this type of refrigerationsystem, a portion of refrigerant leaving a condenser may be introducedinto an enhanced vapor injection inlet of the compressor afterthrottling, thereby controlling exhaust temperature of the compressorwithout sacrificing system capacity.

SUMMARY OF THE INVENTION

An object of the present disclosure is to solve or at least alleviatethe problems existing in the related art.

In one aspect, a heat exchange system, particularly a refrigerationsystem for an electric transport vehicle, is provided, which includes:an enhanced vapor injection compressor, a condenser, an expansion valveand an evaporator, which are located in a main circuit; wherein the heatexchange system further includes a first branch branched from the maincircuit to an vapor injection port of the compressor at a branch point Pdownstream of the condenser, and a first heat exchange unit and a secondheat exchange unit are further provided in the main circuit between thebranch point P and the expansion valve; and wherein a refrigerantleaving the condenser is divided at the branch point P into a firstportion passing through the first heat exchange unit and the second heatexchange unit from the main circuit, and a second portion passingthrough the first branch to the vapor injection port, and wherein thesecond portion of the refrigerant passes through a branch expansionvalve and exchanges heat in the first heat exchange unit with the firstportion of the refrigerant in the main circuit, and the first portion ofthe refrigerant exchanges heat in the second heat exchange unit with arefrigerant flowing from the evaporator to an inlet of the compressor.

Optionally, according to some embodiments of the heat exchange system,the first heat exchange unit and the second heat exchange unit areindependent heat exchangers.

Optionally, according to some embodiments of the heat exchange system,the first heat exchange unit and the second heat exchange unit areincluded in an integrated combined heat exchanger.

Optionally, according to some embodiments of the heat exchange system,the combined heat exchanger includes: a main flow path, which extendsbetween an inlet of the main flow path and an outlet of the main flowpath, and which includes a first portion located in the first heatexchange unit and a second portion located in the second heat exchangeunit; a first heat-exchange flow path, which extends between an inlet ofthe first heat-exchange flow path and an outlet of the firstheat-exchange flow path, and which exchanges heat in the first heatexchange unit with the first portion of the main flow path; and a secondheat-exchange flow path, which extends between an inlet of the secondheat-exchange flow path and an outlet of the second heat-exchange flowpath, and which exchanges heat in the second heat exchange unit with thesecond portion of the main flow path.

Optionally, according to some embodiments of the heat exchange system,the combined heat exchanger is a plate heat exchanger.

Optionally, according to some embodiments of the heat exchange system,the first branch further includes a check valve disposed between thefirst heat exchange unit and the vapor injection port of the compressor,and a first pressure sensor and a first temperature sensor between thefirst heat exchange unit and the check valve, so as to calculate asuperheat degree of the refrigerant leaving the first heat exchange unitin the first branch, wherein the branch expansion valve is an electronicexpansion valve which has a controller, the controller has a built-inpreset value of branch superheat degree, and the controller isconfigured to control an opening degree of the branch expansion valve sothat an actual superheat degree of the refrigerant leaving the firstheat exchange unit in the first branch path approaches the preset valueof the branch superheat degree.

Optionally, according to some embodiments of the heat exchange system,the heat exchange system further includes a second temperature sensorthat monitors a compressor outlet temperature, and the controller of thebranch expansion valve is further configured to increase the openingdegree of the branch expansion valve when a temperature sensed by thesecond temperature sensor is greater than a predetermined value.

Optionally, according to some embodiments of the heat exchange system,in the first heat exchange unit, the second portion of the refrigerantflows in the same direction as or the opposite direction to the firstportion of the refrigerant in the main circuit, and/or, in the secondheat exchange unit, the first portion of the refrigerant flows in thesame direction as or the opposite direction to the refrigerant flowingfrom the evaporator to the inlet of the compressor.

In another aspect, a combined heat exchanger is provided, whichincludes: a first heat exchange unit and a second heat exchange unit; amain flow path, which extends between an inlet of the main flow path andan outlet of the main flow path, and which includes a first portionlocated in the first heat exchange unit and a second portion located inthe second heat exchange unit; a first heat-exchange flow path, whichextends between an inlet of the first heat-exchange flow path and anoutlet of the first heat-exchange flow path, and which exchanges heat inthe first heat exchange unit with the first portion of the main flowpath; and a second heat-exchange flow path, which extends between aninlet of the second heat-exchange flow path and an outlet of the secondheat-exchange flow path, and which exchanges heat in the second heatexchange unit with the second portion of the main flow path.

Optionally, according to some embodiments of the combined heatexchanger, the combined heat exchanger is a plate heat exchanger.

In further another aspect, a method for optimizing a heat exchangesystem, particularly a method for optimizing a refrigeration system foran electric transport vehicle, is provided. The heat exchange systemincludes: an enhanced vapor injection compressor, a condenser, anexpansion valve and an evaporator, which are located in a main circuit;wherein the heat exchange system further includes a first branchbranched from the main circuit to an vapor injection port of thecompressor at a branch point P downstream of the condenser, and a firstheat exchange unit and a second heat exchange unit are further providedin the main circuit between the branch point P and the expansion valve;the method includes: dividing a refrigerant leaving the condenser at thebranch point P into a first portion passing through the first heatexchange unit and the second heat exchange unit from the main circuit,and a second portion passing through the first branch to the vaporinjection port; causing the second portion of the refrigerant to passthrough a branch expansion valve and exchange heat in the first heatexchange unit with the first portion of the refrigerant in the maincircuit; and causing the first portion of the refrigerant to exchangeheat in the second heat exchange unit with the refrigerant flowing fromthe evaporator to an inlet of the compressor.

Optionally, the branch expansion valve is an electronic expansion valve,and the method includes: controlling an opening degree of the electronicexpansion valve based on a preset value of branch superheat degree andan actual superheat degree of the refrigerant leaving the first heatexchange unit in the first branch; and increasing the opening degree ofthe electronic expansion valve when a compressor outlet temperature isgreater than a predetermined value.

BRIEF DESCRIPTION OF THE DRAWINGS

The contents of the present disclosure will become easier to understandwith reference to the accompanying drawings. It can be easily understoodby those skilled in the art that the drawings are merely used forillustration, and are not intended to limit the scope of protection ofthe present disclosure. In addition, like parts are denoted by likenumerals in the drawings, wherein:

FIG. 1 is a schematic structural view of a heat exchange systemaccording to an embodiment of the present disclosure;

FIG. 2 shows another embodiment of a heat exchanger according to anembodiment of the present disclosure;

FIG. 3 shows a curve of a superheat degree and a compressor outlettemperature according to an embodiment of the present disclosure; and

FIG. 4 shows a comparison of a heat exchange system according to anembodiment of the present disclosure with a conventional system in termsof capacity and efficiency.

DETAILED DESCRIPTION OF THE EMBODIMENT(S) OF THE INVENTION

First, referring to FIG. 1 , a heat exchange system according to anembodiment of the present disclosure will be described. The system maybe used in various working conditions, especially for a refrigerationsystem for an electric transport vehicle. The electric transport vehiclerefers to a vehicle powered by a power battery, which is more sensitiveto energy consumption. The heat exchange system includes an enhancedvapor injection compressor 1, a condenser 2, an expansion valve 5 and anevaporator 6, which are located in a main circuit. The enhanced vaporinjection compressor 1 includes a compressor inlet 11, a compressoroutlet 12 and an vapor injection port 13. As shown in the figure, ahigh-temperature, high-pressure vapor leaving the compressor outlet 12of the heat exchange system is separated by an oil separator 15. The oilseparated by oil separator 15 returns to the compressor inlet 11 throughan oil return pipe and a gas-liquid separator 14 while a refrigerantenters the condenser 2. After leaving the condenser 2, the refrigerantpasses through a liquid storage dryer 21, then exchanges heat with asubcooling section of the condenser 2, and passes through a sight glass22 to reaches a branch point P. At the branch point P downstream of thecondenser 2, a first branch 32 is branched from the main circuit to thevapor injection port 13 of the compressor 1, and a first heat exchangeunit 41 and a second heat exchange unit 42 are provided in the maincircuit between the branch point P and the expansion valve 5. Therefrigerant from the condenser 2 is divided at the branch point P into afirst portion passing through the first heat exchange unit 41 and thesecond heat exchange unit 42 from the main circuit 30, and a secondportion passing through the first branch 32 to the vapor injection port33, wherein the second portion of the refrigerant passes through abranch expansion valve 33 and exchanges heat in the first heat exchangeunit 41 with the first portion of the refrigerant in the main circuit,and the first portion of the refrigerant exchanges heat in the secondheat exchange unit 42 with a refrigerant flowing from the evaporator 6to the compressor inlet 11. By allowing the refrigerants to exchangeheat in the first heat exchange unit 41 and the second heat exchangeunit 42 in sequence before entering the expansion valve 5, asupercooling degree of the refrigerant before entering the expansionvalve 5 is increased, and efficiency and capacity of the heat exchangesystem are improved, thereby improving the performance and energyconsumption of heat exchange system. In addition, since the temperatureat the compressor outlet 12 is related to the superheat degree of therefrigerant entering the compressor through the vapor injection port 13,the superheat degree of the refrigerant entering the vapor injectionport 13 of the compressor 1 can be adjusted by controlling an openingdegree of the branch expansion valve 33, thereby controlling thecompressor outlet temperature. Finally, because the branch expansionvalve 33 is used, the first branch can keep its operation, thus avoidingthe effect resulted from the space between a check valve and the vaporinjection port 13 on the compressor efficiency. In this thermal cyclesystem, the refrigerant passes through the expansion valve 5 and theevaporator 6 after passing through the first heat exchange unit 41 andthe second heat exchange unit 42, and the refrigerant leaving theevaporator 6 passes through the second heat exchange unit 42 and thenreturns to compressor inlet 11. The heat exchange system may furtherinclude a second branch 10 communicating with the compressor outlet 12and used for defrosting. The second branch 10 includes a hot gas valve18 which, in a defrosting mode, is opened to allow the high-temperaturegas from the compressor outlet 12 to exchange heat with the evaporator 6for defrosting; the gas is finally passed between the expansion valve 5and the evaporator 6 in the main circuit. In addition, a low-pressureswitch 71 may be provided upstream of the compressor inlet 11, and ahigh-pressure switch may be provided downstream of the compressor outlet12.

In some embodiments, the first heat exchange unit 41 and the second heatexchange unit 42 are included in an integrated combined heat exchanger4, the structures of the first heat exchange unit 41 and the second heatexchange unit 42 may be simplified through such a design, and pipelinesand joints connecting the first heat exchange unit 41 and the secondheat exchange unit 42 may be omitted. In some embodiments, the combinedheat exchanger 4 includes: a main flow path 43, which extends between aninlet 431 of the main flow path and an outlet 432 of the main flow path,and which includes a first portion located in the first heat exchangeunit 41 and a second portion located in the second heat exchange unit42; a first heat-exchange flow path 44, which extends between an inlet441 of the first heat-exchange flow path and an outlet 442 of the firstheat-exchange flow path, and which exchanges heat in the first heatexchange unit 41 with the first portion of the main flow path 43; and asecond heat-exchange flow path 45, which extends between an inlet 451 ofthe second heat-exchange flow path and an outlet 452 of the secondheat-exchange flow path, and which exchanges heat in the second heatexchange unit 42 with the second portion of the main flow path 43. Inthe embodiment shown in the figure, in the first heat exchange unit 41,the two streams of fluid flow in the same direction during heatexchange, that is, the fluid in the first portion of the main flow path43 and the fluid in the first heat-exchange flow path 44 flow from rightto left during heat exchange; and in the second heat exchange unit 42,the two streams of fluid flow in opposite directions during heatexchange, that is, the fluid in the second portion of the main flow pathflows from right to left during heat exchange, and the fluid in thesecond heat-exchange flow path 45 flows from left to right during heatexchange. In some other embodiments, the two streams of fluid in the twoheat exchange units may either flow in opposite directions or in thesame direction during heat exchange.

In some embodiments, the first branch 32 further includes a check valve36 disposed between the first heat exchange unit 41 and the vaporinjection port 13 of the compressor, and a first pressure sensor 34 anda first temperature sensor 35 between the first heat exchange unit 41and the check valve 36, so as to calculate a superheat degree of therefrigerant leaving the first heat exchange unit 41 in the first branch.The branch expansion valve 33 is an electronic expansion valve which hasa controller, the controller of the branch expansion valve 33 has abuilt-in preset value of branch superheat degree, such as SH=5 or SH=10or the like, and the controller is configured to control an openingdegree of the branch expansion valve 33 so that an actual superheatdegree of the refrigerant leaving the first heat exchange unit 41 in thefirst branch path approaches the preset value of the branch superheatdegree. For example, when the superheat degree of the refrigerantleaving the first heat exchange unit 41 in the first branch 32calculated based on the first pressure sensor 34 and the firsttemperature sensor 35 is greater than the preset value, the openingdegree of the branch expansion valve 33 is increased; otherwise, theopening degree of the branch expansion valve 33 is decreased. On theother hand, the heat exchange system may further include a secondtemperature sensor 17 that monitors the temperature of the compressoroutlet 12, and a second pressure sensor 16. The controller of the branchexpansion valve 33 is further configured to increase the opening degreeof the branch expansion valve 33 when the temperature sensed by thesecond temperature sensor 17 is greater than a predetermined value,thereby controlling the compressor outlet temperature to be lower thanthe set predetermined value.

Continued reference is made to FIG. 2 , which shows another embodimentaccording to the present disclosure. In this embodiment, the first heatexchange unit 41 and the second heat exchange unit 42 are separate heatexchangers, wherein the main flow path 43 includes a first portion 434in the first heat exchange unit 41 and a second portion 435 in thesecond heat exchange unit 42, and the first portion 434 and the secondportion 435 are connected by a pipeline 433. In such an embodiment, thefirst heat exchange unit 41 and the second heat exchange unit 42 areindependent from each other and do not interfere with each other, butadditional pipelines and joints related to the pipeline 433 are needed.

Referring to FIG. 3 , a relationship between the superheat degree of therefrigerant in the first branch and the compressor outlet temperatureaccording to the embodiment of the present disclosure is shown. It canbe seen that whatever frequency the compressor is operating at, as longas the superheat degree of the refrigerant leaving the first heatexchange unit in the first branch is reduced, the compressor outlettemperature can be reduced. Therefore, the compressor outlet temperaturecan be kept below a predetermined value by adjusting the opening degreeof the branch expansion valve.

Continued reference is made to FIG. 4 , which shows a comparison of theheat exchange system according to the embodiment of the presentdisclosure with two types of heat exchange systems. In the system 1, aportion of the refrigerant from the condenser passes through aninjection valve and a one-way valve to the vapor injection port of theenhanced vapor injection compressor, and the other portion of therefrigerant, before entering the evaporator, exchanges heat with therefrigerant directed to the inlet of the compressor from the evaporator.In the system 2, a portion of the refrigerant from the condenser passesthe expansion valve, then exchanges heat with the refrigerant directedto the evaporator, and then passes through the one-way valve to thevapor injection port of the enhanced vapor injection compressor. It canbe seen that the heat exchange system according to the presentdisclosure has a stronger capacity and higher efficiency than the system1 and the system 2, and is particularly suitable for an electrictransport vehicle that is sensitive to energy consumption.

In another aspect, a method for optimizing a heat exchange system,particularly a method for optimizing a refrigeration system for anelectric transport vehicle, is provided. The heat exchange systemincludes: an enhanced vapor injection compressor 1, a condenser 2, anexpansion valve 5 and an evaporator 6, which are located in a maincircuit; wherein the heat exchange system further includes a firstbranch 32 branched from the main circuit to an vapor injection port ofthe compressor at a branch point P downstream of the condenser, and afirst heat exchange unit 41 and a second heat exchange unit 42 arefurther provided in the main circuit between the branch point P and theexpansion valve 5; the method includes: dividing a refrigerant leavingthe condenser at the branch point P into a first portion passing throughthe first heat exchange unit and the second heat exchange unit from themain circuit, and a second portion passing through the first branch tothe vapor injection port; causing the second portion of the refrigerantto pass through a branch expansion valve and exchange heat in the firstheat exchange unit with the first portion of the refrigerant in the maincircuit; and causing the first portion of the refrigerant to exchangeheat in the second heat exchange unit with the refrigerant flowing fromthe evaporator to an inlet of the compressor. In some embodiments, thebranch expansion valve is an electronic expansion valve, and the methodincludes: controlling an opening degree of the electronic expansionvalve based on a preset value of branch superheat degree and an actualsuperheat degree; and increasing the opening degree of the electronicexpansion valve when a compressor outlet temperature is greater than apredetermined value.

Various specific embodiments of the present disclosure have beendescribed above. It should be understood that the scope of the presentdisclosure is not limited to the illustrated embodiments and is definedby the claims. Modifications or variations that do not depart from theconcept of the present disclosure should also be included within thescope of the present disclosure.

What is claimed is:
 1. A combined heat exchanger, comprising: a firstheat exchange unit and a second heat exchange unit; a main flow path,which extends between an inlet of the main flow path and an outlet ofthe main flow path, and which comprises a first portion located in thefirst heat exchange unit and a second portion located in the second heatexchange unit; a first heat-exchange flow path, which extends between aninlet of the first heat-exchange flow path and an outlet of the firstheat-exchange flow path, and which exchanges heat in the first heatexchange unit with the first portion of the main flow path; and a secondheat-exchange flow path, which extends between an inlet of the secondheat-exchange flow path and an outlet of the second heat-exchange flowpath, and which exchanges heat in the second heat exchange unit with thesecond portion of the main flow path.
 2. The combined heat exchangeraccording to claim 1, wherein the combined heat exchanger is a plateheat exchanger.
 3. A method for optimizing a heat exchange system,particularly a method for optimizing a refrigeration system for anelectric transport vehicle, the heat exchange system comprising: anenhanced vapor injection compressor, a condenser, an expansion valve andan evaporator, which are located in a main circuit; wherein the heatexchange system further comprises a first branch branched from the maincircuit to an vapor injection port of the compressor at a branch point Pdownstream of the condenser, and a first heat exchange unit and a secondheat exchange unit are further provided in the main circuit between thebranch point P and the expansion valve; the method comprising: dividinga refrigerant leaving the condenser at the branch point P into a firstportion passing through the first heat exchange unit and the second heatexchange unit from the main circuit, and a second portion passingthrough the first branch to the vapor injection port; causing the secondportion of the refrigerant to pass through a branch expansion valve andexchange heat in the first heat exchange unit with the first portion ofthe refrigerant in the main circuit; and causing the first portion ofthe refrigerant to exchange heat in the second heat exchange unit withthe refrigerant flowing from the evaporator to an inlet of thecompressor.
 4. The method according to claim 3, wherein the branchexpansion valve is an electronic expansion valve, and the methodcomprises: controlling an opening degree of the electronic expansionvalve based on a preset value of branch superheat degree and an actualsuperheat degree of the refrigerant leaving the first heat exchange unitin the first branch; and increasing the opening degree of the electronicexpansion valve when a compressor outlet temperature is greater than apredetermined value.